The first 1.5–2 years of the war turned out extremely unsuccessfully for the Red Army. Why did this happen? Among all the reasons, the main one is the leadership of the USSR ignoring the achievements of military science. In the early 1930s. In the USSR, a new theory of warfare was developed - the theory of deep operations. But the fate of this theory in the Soviet Union turned out to be tragic. In the confrontation between horsemen and tankers, the horsemen gained the upper hand, and therefore they called this theory “the theory of deep betrayal.” And German generals borrowed this theory to arm the German Wehrmacht. Having used it for the first time in the German-Polish war in September 1939, he achieved stunning results - he defeated a million-strong Polish army in 16 days. The German experience in waging this war was analyzed in the book “New Forms of Struggle,” published in Military Publishing House in 1940, in which he wrote that the Germans would use the same strategy in future wars. But the military and political leadership of the USSR ignored this warning.